Medical devices are becoming increasingly complex in terms of function and geometry. It has been recognized that imparting desirable properties to the surface of medical devices, in particular small implantable medical devices, by coating the surface of the device with one or more compounds can enhance the function and effectiveness of the medical device. Traditional coating methods, such as dip coating, are often undesirable for coating these complex geometries since coating solution may get entrapped in the device structure. This entrapped solution may cause webbing or bridging of the coating solution and may hinder the device from functioning properly.
Spray coating techniques have also been used to apply coating material to various devices, including medical devices. However, current methods of spray coating these devices are often problematic and result in reduced coating consistency and reduced coating efficiency. One problem associated with spray coating techniques is related to excess spray, or “overspray”, that is deposited on non-target locations during the coating process. Overspray can result in wasting of the coating material and can also lend to inaccuracies and defects during the process. This problem often occurs when small devices are coated, in particular small medical devices, such as stents and catheters.
Inaccuracies in the coating process can also be manifested in variable amounts of the coated material being deposited on the surface of the device. When a pharmaceutical agent is included in the coating material, it is often necessary to deliver precise amounts of the agent to the surface of the device to ensure that a subject receiving the coated device receives a proper dose of the agent. It has been difficult to achieve a great degree of accuracy using traditional coating methods and machines.
The drying of the applied coating and the manipulation of the devices after application of a coating can also be problematic aspects of the coating process, particularly processes that involve the coating of devices having multi-dimensional surfaces. Typically, a coating process involves repetitively applying a coating material to a fixtured device in order to achieve a target quantity and quality of coated material. Devices are often manipulated between the applications of the coating material and dried to a certain extent before these manipulations are performed. The drying of applied coatings and manipulation of the device can lead to defects in the coating on the device and can also lead to an increased time for the coating procedure.
Accordingly, there is a need for new equipment and methods useful for overcoming the problems associated with the spray coating procedures, in particular, the spray coating of small medical devices.